1. Field of the Invention
The present invention relates in general to deployment brakes operative during the opening of parachute canopies and, more particularly, to a deployment brake release system that is configurable for use with canopies of different types and sizes.
2. Description of the Related Art
Precision cargo delivery relies upon unmanned aerial vehicles (UAVs) to guide cargo parachutes to preselected GPS coordinates. The UAV includes an airborne guidance unit (AGU) having a structural frame that contains at least one battery, a motor, an avionics computer with GPS receiver, a motor controller, a processor, etc. A compass or other rate sensing instrument may also be included.
The precision cargo delivery parachute systems are similar to those used in personnel parachutes and can include low gliding round parachutes and higher gliding ram-air parachutes, as well as cruciform parachutes of the type disclosed in U.S. Pat. No. 6,443,396. Often the parachute systems have many operational procedures that are normally carried out by personnel and therefore must be automated in the cargo setting. One such operational procedure is the release of the deployment brakes after full inflation.
During parachute deployment, at least part of the trailing edge of the canopy is deflected. Such deflection is effected by the same mechanism used to steer the canopy once it is in flight. For example, to turn the parachute to the left while in flight, one or more steering suspension lines connected to the trailing edge on the left side of the canopy are shortened, i.e., pulled downwardly, by the motor in the AGU. This shortening deflects the corresponding trailing edge and causes the parachute to turn left. In the case of initial deployment, suspension lines attached along nearly all of the trailing edge act as brake lines and are held in a shortened configuration. The resulting trailing edge deflection prevents the canopy from rocking back and forth and provides greater canopy stability during inflation.
Peak load on the brake/suspension lines occurs during initial inflation when opening forces and the rate of deceleration are the greatest. To withstand the peak load, the motor attached to the brake/suspension lines must be relatively heavy duty which increases cost and weight, both of which are undesirable characteristics in parachute product design.
To overcome this difficulty, prior art approaches have secured the brake/suspension lines to the frame of the AGU with connection lines having associated pyrotechnic cutting devices. Once the canopy has fully inflated to the extent possible in this deployment configuration, the pyrotechnic cutters are activated to sever the connection lines and thereby release the trailing edge. While this can be effective, pyrotechnic devices require proper timing and add unwanted complexity and expense, particularly in the context of routine and repeated airborne delivery of equipment and supplies such as is needed for troop support during military operations.
Accordingly, a need exists for a deployment brake release system that is simpler and less expensive than the prior art approaches, while offering highly reliable and reusable operation.